示例：离群值移除

使用 trim 函数可在处理数据集之前从中移除离群值。

1. 定义描述热流的数据集。

2. 使用 Grubbs 函数检验离群值。

3. 创建包含离群值索引的矢量。

4. 为 y 数据集的每行分配一个编号。

5. 移除离群值。

datanew 数组的行数比原始数据集的行数少：

6. 绘制原始数据集和裁剪后的数据集的图像。

<region id="ID0EXRVU" top="652.80000000000007" left="19.200000000000003" height="262.306263683696" width="577" xmlns="http://schemas.mathsoft.com/worksheet50">
  <plot background-type="white" origin-positioning="true">
    <xyPlot>
      <title class="- topic/title " wwtype:type="Paragraph" xmlns:wwtype="urn:WebWorks-Type-Schema" />
      <legend />
      <traces>
        <trace resultRef="81">
          <traceStyle color="#FF008000" symbol="rectangle" line-weight="1" line-style="None">lines</traceStyle>
        </trace>
        <trace resultRef="82">
          <traceStyle color="#FFFF0000" symbol="plus" line-weight="1" line-style="None">lines</traceStyle>
        </trace>
      </traces>
      <graph-size width="419.4" height="166.306263683696" />
      <axes>
        <xAxis rank="1" legend-position="PlotBoundaryBottom" start="0" end="200">
          <axisLine position="bottom" positionticmark="-1" legendWidth="124.943333333333" />
          <axisGrid>
            <gridFrequency>11</gridFrequency>
            <gridLabels display="true" />
            <gridLines />
            <tickMarks display="true" />
          </axisGrid>
          <axisLabel />
          <markers />
          <numberFormat>
            <decimal precision="3" show-trailing-zeros="false" radix="dec" imaginary-value="i" />
          </numberFormat>
          <plotEquations>
            <plotEquation>
              <math resultRef="87">
                <id xml:space="preserve" xmlns="http://schemas.mathsoft.com/math50">x</id>
              </math>
              <math resultRef="88">
                <placeholder xmlns="http://schemas.mathsoft.com/math50" />
              </math>
            </plotEquation>
            <plotEquation>
              <math resultRef="89">
                <apply xmlns="http://schemas.mathsoft.com/math50">
                  <matcol />
                  <id xml:space="preserve">datanew</id>
                  <real>0</real>
                </apply>
              </math>
              <math resultRef="90">
                <placeholder xmlns="http://schemas.mathsoft.com/math50" />
              </math>
            </plotEquation>
          </plotEquations>
          <xyDomain scale-type="linear" auto-scale="true">
            <startValue resultRef="84">
              <real xmlns="http://schemas.mathsoft.com/math50">0</real>
            </startValue>
            <endValue resultRef="86">
              <real xmlns="http://schemas.mathsoft.com/math50">200</real>
            </endValue>
          </xyDomain>
        </xAxis>
        <yAxis rank="1" legend-position="PlotBoundaryLeft" start="9.17" end="9.39">
          <axisLine position="origin" positionticmark="0" legendWidth="124.943333333333" />
          <axisGrid>
            <gridFrequency>12</gridFrequency>
            <gridLabels display="true" />
            <gridLines />
            <tickMarks display="true" />
          </axisGrid>
          <axisLabel />
          <markers />
          <numberFormat>
            <decimal precision="3" show-trailing-zeros="false" radix="dec" imaginary-value="i" />
          </numberFormat>
          <plotEquations>
            <plotEquation>
              <math resultRef="95">
                <id xml:space="preserve" xmlns="http://schemas.mathsoft.com/math50">y</id>
              </math>
              <math resultRef="96">
                <placeholder xmlns="http://schemas.mathsoft.com/math50" />
              </math>
            </plotEquation>
            <plotEquation>
              <math resultRef="97">
                <apply xmlns="http://schemas.mathsoft.com/math50">
                  <matcol />
                  <id xml:space="preserve">datanew</id>
                  <real>1</real>
                </apply>
              </math>
              <math resultRef="98">
                <placeholder xmlns="http://schemas.mathsoft.com/math50" />
              </math>
            </plotEquation>
          </plotEquations>
          <xyDomain scale-type="linear" auto-scale="true">
            <startValue resultRef="92">
              <real xmlns="http://schemas.mathsoft.com/math50">9.17</real>
            </startValue>
            <endValue resultRef="94">
              <real xmlns="http://schemas.mathsoft.com/math50">9.37</real>
            </endValue>
          </xyDomain>
        </yAxis>
      </axes>
    </xyPlot>
  </plot>
</region>

预计离群值会偏离结果时，可将它们移除以提高结果精度。对于热流数据：

无论数据中是否存在离群值，平均值基本上会保持不变，但标准差会减小。这一变化将显著影响数据模型。